title: Biodegradation of p-nitrophenol in an aqueous waste stream by immobilized bacteria.
abstract: Microbiological analyses of activated sludge reactors after repeated exposure to 100 mg of p-nitrophenol (PNP) per liter resulted in the isolation of three Pseudomonas species able to utilize PNP as a sole source of carbon and energy. Cell suspensions of the three Pseudomonas sp., designated PNP1, PNP2, and PNP3, mineralized 70, 60, and 45% of a 70-mg/liter dose of PNP in 24, 48, and 96 h, respectively. Mass-balance analyses of PNP residues for all three cultures showed that undegraded PNP was less than 1% (less than 50 micrograms); volatile metabolites, less than 1%; cell residues, 8.4 to 14.9%; and water-soluble metabolites, 1.2 to 6.7%. A mixed culture of all three PNP-degrading Pseudomonas sp. was immobilized by adsorption onto diatomaceous earth biocarrier in a 1.75-liter Plexiglas column. The column was aerated and exposed to a synthetic waste stream containing 629 to 2,513 mg of PNP per liter at flow rates of 2 to 15 ml/min. Chemical loading studies showed that the threshold concentration for acute toxicity of PNP to the immobilized bacteria was 2,100 to 2,500 mg/liter. Further studies at PNP concentrations of 1,200 to 1,800 mg/liter showed that greater than 99 and 91 to 99% removal of PNP was achieved by immobilized bacteria at flow rates of 10 and 12 ml/min, respectively. These values represent hydraulic retention times of 48 to 58 min and PNP removal rates of 0.99 to 1.1 mg/h per g of biocarrier at 25 degrees C under optimal conditions. This study shows the successful use of immobilized bacteria technology to remove high concentrations of PNP from aqueous waste streams.
authors.affiliation: Environmental Sciences Center, Monsanto Company, St. Louis, Missouri 63167.
authors.forename: M A
authors.initials: MA
authors.lastname: Heitkamp
authors.forename: V
authors.initials: V
authors.lastname: Camel
authors.forename: T J
authors.initials: TJ
authors.lastname: Reuter
authors.forename: W J
authors.initials: WJ
authors.lastname: Adams
mesh_terms: D000327:Adsorption; D001673:Biodegradation, Environmental; D009596:Nitrophenols / Q000378:metabolism*; D011549:Pseudomonas / Q000302:isolation & purification / Q000378:metabolism*; D012722:Sewage; D012988:Soil Microbiology; D014871:Water Microbiology
chemical_list: D009596:Nitrophenols; D012722:Sewage; C024836:4-nitrophenol